Why do certain body shape and size relationships remain consistent over long periods? One such example is found in flies, where small wings are normally rounder than large wings. Researchers from Norway and the United States bred fruit flies to change that relationship as a way to explore the limits of evolution and shed light on a question that biologists have puzzled over for the last 100 years. Throughout the natural world, shape, physiology and behavior are strongly related to the size of the organisms. These relationships are found both within species and between species, and often remain unchanged in species separated for millions of years. For example, the hearts of small species beat much faster than those of large species, and the antlers of small deer species are smaller, relative to body size, compared to antlers of large species. Sometimes these relationships are so strong that they are considered to be laws of nature, so much so that generations of biologists over the last 100 years have wondered whether or not these relationships can be changed by natural selection. In a paper published online on September 14, 2015 in PNAS, researchers from the Norwegian University of Science and Technology's Center for Biodiversity Dynamics (CBD), the Centre for Evolutionary and Ecological Synthesis at the University of Oslo, and Florida State University now say that the answer to this question is both yes (in principle), but no (in practice). The article is titled “Complex Constraints on Allometry Revealed by Artificial Selection on the Wing of Drosophila melanogaster.” "Our results suggest that these traits can evolve, but changing these relationships creates deleterious side effects for the organism.Login Or Register To Read Full Story